Question

I am currently designing an app with the Metro app framework which includes a live video chat feature. I am using the GrayscaleTransform MFT included in the MediaCapture sample (at this point simply copy-and-pasted from the sample).

However, when I try to add the grayscale effect to the camera’s image stream, I get a “class not registered” fatal error. I understand this is because I must ‘activate and register’ the media extension, but I do not know how. How do I register the media extension?

All help is greatly appreciated and I always accept an answer!

UPDATE: My GrayScale IDL file is shown below:

import "Windows.Media.idl";

#include <sdkddkver.h>

namespace GrayscaleTransform
{
[version(NTDDI_WIN8), activatable(NTDDI_WIN8)]
runtimeclass GrayscaleEffect 
{
    [default] interface Windows.Media.IMediaExtension;
}
}

Answer 1

The media extension is specified as an <Extension> (or extensibility point) in the package manifest’s Extensions section, but you need to insert it manually (i.e. open the appxmanifest as code instead of double-clicking.)

Using the GrayscaleTransform example, in the Media extensions sample, open the MediaExtensions project’s package.appxmanifest (as code) and look for this in the <Extensions> section:

<Extension Category="windows.activatableClass.inProcessServer">
    <InProcessServer>
        <Path>GrayscaleTransform.dll</Path>
        <ActivatableClass ActivatableClassId="GrayscaleTransform.GrayscaleEffect" ThreadingModel="both" />
    </InProcessServer>
</Extension>

There’s a bit more general info on extensions in App contracts and extensions.